Influence of survivin knockdown on apoptotic rate of chondrosarcoma cells. Influences of RNA interference against survivin on programmed cell death of SW1353 (A and B) and Hs819.T (C and D) were measured by caspase 3/7 activity (A and C) and by analysing the sub-G0/1-phase fraction by using the fluorescence-activated cell sorting-propidium iodide staining method (B and D). Survivin knockdown resulted in moderate elevations of the indicators of apoptotic activity in SW 1353 (A and B, left) but not in Hs819.T (C and D). Transfection of GFP had no significant effects on apoptosis. Pronounced elevations of apoptotic markers were seen when the cells were stressed with doxorubicin 5 μM over 24 hours (A - D, right). The cytotoxic treatment resulted in a substantial increase of caspase 3/7 activity and fraction of apoptotic cells. Suppression of survivin sensitized the cells to doxorubicin treatment and further increased the apoptotic activity significantly in both cell lines. Again, transfection of GFP siRNA was used as a control. The error bars represent +/-SEM. P values less than 0.05 were considered significant (*). The original results of one representative experiment are shown.